The prior art is aware of various fluid systems for directing fluid flow to and from fluid motors, and it is also aware of various arrangements of fluid valves for the purpose mentioned. Prior U.S. patents which show some type of hydraulic system are Nos. 2,386,291 and 2,423,264 and 2,466,485 and 3,370,602. These patents only show arrangements of hydraulic or fluid systems which employ a driven member or motor and a valve for controlling flow thereto, and the last three patents mentioned also show a pump and an equalizing or diverter valve in addition to a type of control valve in the system.
The prior art also reveals various arrangements for fluid valves, such as seen in U.S. Pat. Nos. 2,593,185 and 2,971,552 and 3,060,953 and 3,200,830 and 3,437,103 and 3,554,213 and 3,590,844 and 3,722,524 and 3,924,650. These patents all show various arrangements for valves having spools serving as closure members and with the spools being responsive to the fluid pressure within the valve itself. However, these valves are fundamentally only flow divider valves where flow will enter the valve in one opening and will leave the valve through two other openings. In that regard, the latter three of the first aforesaid group of patents also show divider valves, and U.S. Pat. Nos. 2,466,485 and 3,370,602 particularly show spools with end faces thereon disposed in separated chambers within the valve body and having passageways leading to the chambers, all for shifting the spool according to fluid pressure on those spool faces. However, those are still only diverter valves, rather than a combiner type of valve which, as in the present instance, takes fluid from two sources and combines it in an outlet flow. As such, this is the advantage and object of the present invention.
However, U.S. Pat. No. 3,437,103 can be used as a combiner type of valve where the fluid is taken from two sources and combines it into one outlet. Nevertheless, that prior art does not disclose a combiner wherein a fluid is accepted from two sources and combined at some flow proportion to an outlet, and thus it does not select fluid from one of two sources to direct it to the desired outlet or user system. As such, the present invention has as its object the provision of a valve which receives fluid from two sources and, at some proportionate pressure or flow between the two sources, the valve reacts to direct the flow from one source and to direct only it to the user system. Further, this invention has as its objective the accomplishment of the aforementioned improvements by utilization of simplified apparatus, such as the self-responsive selector valve mentioned, which is readily and easily inserted into a fluid system of a pump, a control valve and a fluid motor.
Still further, it is an object and advantage of this invention to provide apparatus wherein a self-responsive valve is incorporated in a system and arranged so that when the powered element of the system requires excessive fluid, the valve will react and in essence re-cycle the fluid through the powered element or apparatus itself. Simultaneous with that action, the self-responsive valve of this invention will divert the flow from the supplying pump and to the reservoir. Therefore, the apparatus of this invention is particularly useful in situations such as vehicle transmissions, and particularly tractor transmissions where, for instance, when the tractor is running downhill and the transmission is thus driven through that type of movement, the fluid motor arranged with the transmission will cause excessive flow of the fluid, and that fluid can be diverted through the valve employed herein and back to the driven motor itself, to thus avoid anti-cavitation of the system. When the cavitation of the drive motor of the aforementioned system occurs, complete loss of vehicle or tractor speed control results, and thus the apparatus of this invention is utilized to avoid that uncontrolled condition. Some of the prior art attempts to solve this problem result in an arrangement where there is only one available downhill tractor speed, or there may be an arrangement for excessive loading of the engine itself, or there may be an arrangement to provide for only a short time duration of downhill control. However, the present invention provides for the complete and self-responsive control of the tendency for the system to cavitate, as mentioned.
Other objects and advantages will become apparent upon reading the following description in light of the accompanying drawings.